HADEES -Ali is the master of successors

 ‘God did not create anything unless He made a master in it. The eagle is the master of the birds. The bull is the master of beasts. The lion is the master of wild animals. Friday is the master of the days of the week. Ramadan is the master of the months. Israfil is the master of the angels. Adam is the master of the humans. I am the master of the Prophets and Ali is the master of successors.'  

The Prophet (saws) 

Beharul-Anwaar, vol.40 p.46